As an American writer,Mark Twain,once said,“Everybody talks

As an American writer,Mark Twain,once said,“Everybody talks about the weather,but nobody does anything about it.” It is true that everybody talks about the weather.Many people begin their talks by saying,“Isn’t it a nice（1）day / weather?” “Do you think it will rain?” “I think it’s going to rain tomorrow.” Another man will say,“Yes,it’s cloudy in the east.We are going to have fine weather tomorrow.”
答案是day,我想知道为什么不是 weather.请详解.